Implications of genotype-by-environment interactions in maize(zea mays L.)variery selection using mother and baby trials
Date
2011-03-30
Authors
Nginamau, Dibanzilua
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Abstract
Maize is the main staple food crop in the Southern Africa Development Community
(SADC), which includes Zimbabwe and its productivity increases when improved
varieties are planted. Development of such technologies is mainly by public and private
breeding programs, which in most cases do this in managed stress environments such as
research stations while they are deployed in farmers' fields, which have random stresses.
This situation creates Genotype by Environment (GxE) interactions, which constitute
one of the major complications in plant breeding and has been widely discussed,
particularly in relation to their effect on the choice of selection environment(s) and
indeed the whole selection process. Repeatability of aspects of GxE interactions is an
important factor to be assessed in designing more efficient selection programs.
CIMMYT with collaborating National Agricultural Research Systems (NARSs) in the
SADC region have been using an evaluation scheme, Mother and Baby Trials (MBTs),
to ensure that maize varieties are tested in target environments. In Zimbabwe this testing
has been going on since 1999. Analysis of historical data from these multi-environment
trials over years can be used to provide some clues on how to improve the testing
strategy. Using sequential retrospective pattern analysis based on the SEQRJET package
Versionl.l the historical data from Zimbabwe were analyzed to characterize
environments, the tested genotypes and identify repeatable GxE interactions across
years. The results showed that environments were classified into four groups based on
their similarities. Differences among these groups were mainly due to SWHC, EVAPO
and soil depth as major determinants of favourable soil water status for plant growth.
Elevation and temperature were also important. High grain yield was associated with
environment groups characterized by high SWHC, low EVAPO and deep soil profile.
Genotypes were also classified into four groups. The type of variety underpinned
differences among genotype groups. OPVs, ZM 421, ZM 423 and ZM 521, bred for
stress tolerance were in the same group while the hybrids, which were not specifically
bred for stress tolerance, were in other groups. Varying soil nitrogen levels effectively
created differe-it environments among the locations used. Inclusion of environments
representing important stress in the testing environments improved the effectiveness of
the selection programme in identifying suitable varieties for the conditions characteristic
of farmers' environment in Zimbabwe. Variety testing in Zimbabwe must be
rationalized to cover 16 environments represent two locations in agro-ecological zone II,
one location in zone III, five locations in zone IV and one locations in zone V.
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Keywords
Corn -- SADC--Corn , Corn -- Biothecnology -- SADC , Corn -- Development -- SADC , Environmental Engineering -- SADC